[DOCS] Fix porter stem filter name in other stemming docs

docs/reference/analysis/tokenfilters/keyword-marker-tokenfilter.asciidoc

@@ -26,7 +26,7 @@ index :
             myAnalyzer :
                 type : custom
                 tokenizer : standard
-                filter : [lowercase, protwods, porterStem]    
+                filter : [lowercase, protwods, porter_stem]    
         filter :
             protwods :
                 type : keyword_marker

docs/reference/analysis/tokenfilters/keyword-repeat-tokenfilter.asciidoc

@@ -19,7 +19,7 @@ index :
             myAnalyzer :
                 type : custom
                 tokenizer : standard
-                filter : [lowercase, keyword_repeat, porterStem, unique_stem]    
+                filter : [lowercase, keyword_repeat, porter_stem, unique_stem]    
             unique_stem:
                 type: unique
                 only_on_same_position : true

docs/reference/analysis/tokenfilters/stemmer-override-tokenfilter.asciidoc

@@ -26,7 +26,7 @@ index :
             myAnalyzer :
                 type : custom
                 tokenizer : standard
-                filter : [lowercase, custom_stems, porterStem]    
+                filter : [lowercase, custom_stems, porter_stem]    
         filter:
             custom_stems:
                 type: stemmer_override